The new Willamette River Bridge is 50% complete. The southbound structure (foreground) stands in striking comparison with the original bridge (background). Photos: Oregon DOT

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The new structure is a pair of arched bridges that touches down in the Willamette River once. The concrete arches get their shape and strength from cages made from “#18 vert;” at 13 pounds/foot, the largest rebar available. With such a heavy frame, the arch ribs will tip the scales at more than 11 million pounds (photo below explains how they'll be supported). Here, two crew members put the finishing touches on an arch reinforcement cage.

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With the formwork removed, the beauty and grace of the new Willamette River Bridge is revealed. The weight of the concrete arches is fully supported by large caissons poured deep in the ground on either bank and in the middle of the river.

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Beams of light fall on the southbound bridge, highlighting its elegant arches. Here, crews finalize the new bridge columns and prepare to install the bridge deck.

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Residents of Eugene and Springfield, Ore., track the project's progress from a pedestrian viaduct that crosses the river.

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Before and after: When Oregon's 50-year-old Willamette River Bridge (inset) was deemed structurally deficient, the state used construction manager/general contractor (CM/CG) for the first time to replace the original I-bulb structure with a more attractive deck-arch design pictured in the rendering at top of page. Rendering: OBEC Consulting Engineers

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Completion of the new southbound bridge (shown here from the west) marks the halfway point of the Willamette River Bridge replacement, which is scheduled to be finished in 2013.

After serving West Coast travelers for nearly 50 years, the Interstate 5 bridge over the Willamette River in Eugene, Ore., was in dire need of replacement. During a preliminary inspection in 2002, Oregon DOT engineers identified shear cracks severe enough to require posting weight limits; heavy-haul trucks had to be rerouted 200 miles around the structure until we could complete a temporary replacement in 2004.

Part of the $1.3-billion, 10-year Oregon Transportation Investment Act III State Bridge Delivery Program, the new bridge was going to be a complex project for a number of reasons. Not only is it the largest bridge replacement in our history, it also had the potential for major environmental and community impacts. The new bridge will span nearly 2,000 horizontal feet, 700 of which cross the river. It's flanked by parks on either side and serves two communities with highly engaged residents: Eugene and Springfield.

The National Environmental Policy Act (NEPA) required us to prepare an environmental assessment for the new structure. By the time the finding of “no significant impact” was signed, we had approximately five years to complete design and construction within the state program's legislatively mandated deadline. We had no choice but to accelerate the construction schedule.

We could have used design-build contracting to speed up delivery, as we have on hundreds of bridges across the state, but that would have meant sacrificing control over design decisions.

After analyzing the various procurement methods and researching projects done by other state agencies for vertical construction, we chose to use construction manager/general contractor (CM/CG), otherwise known as construction manager-at-risk (CM@R), for the first time.

Knowing that the Oregon Administrative Rules accommodate alternative contracting methods, we began to assemble an exemption proposal that would meet its requirements, which include ensuring fairness to the contracting community, not hampering competition, and providing value to the state.

To ensure the construction industry was on board, we discussed the concept with members of the Associated General Contractors and the American Council of Engineering Companies. Based on their input, we developed an exemption application that met state criteria and secured signed contracts with the design firm and contractor by the time of the NEPA finding, leaving us poised to start design work almost immediately.